1. Technical Field
The present invention relates to a piezoelectric element composed of a lower electrode film, a piezoelectric layer, and an upper electrode film and a method of manufacturing the piezoelectric element, and more particularly to a piezoelectric element for use in a liquid ejecting head which ejects liquid droplets from its nozzle orifices.
2. Related Art
A piezoelectric element for use in liquid ejecting heads has a structure in which a piezoelectric film made of a piezoelectric material having an electromechanical transduction function is interposed between two electrodes. The piezoelectric film is made of, for example, crystallized piezoelectric ceramic.
An example of liquid ejecting heads using such piezoelectric elements is an ink jet recording head structured in a manner such that part of a pressure generating chamber communicating with a nozzle orifice from which ink droplets are ejected is constituted by a vibrating plate and a piezoelectric element deforms the vibrating plate so as to apply a pressure to ink in the pressure generating chamber, so that ink droplets are ejected from the nozzle orifice. There are two types of commercialized ink jet recording head. One type uses a longitudinal oscillation mode actuator in which a piezoelectric element expands and contracts in an axial direction and the other type uses a flexural oscillation mode actuator. As for the ink jet recording head using the flexural oscillation mode actuator, there is a known technique in which a piezoelectric layer having a uniform thickness is formed over the entire surface of a vibrating plate by a film forming technique and then it is divided into a plurality of piezoelectric units, each having a shape corresponding to that of a pressure generating chamber, by a lithography process. In this technique, piezoelectric elements are disposed so as to correspond to the pressure generating chambers and isolated from each other.
JP-A-2001-274472 discloses a technique in which a piezoelectric layer (piezoelectric thin film) is made of, for example, a ferroelectric substance, such as lead zirconate titanate (PZT). Further, the piezoelectric thin film is prepared by forming titanium crystals on a lower electrode film by a sputtering method and then forming a piezoelectric precursor film on the titanium crystals by a sol-gel method or a metal-organic decomposition (MOD) method (MOD) and calcining the piezoelectric precursor film. Upon calcining the piezoelectric precursor film, the lower electrode film is also heated. However, the above-mentioned document does not disclose details of the lower electrode film nor mention adhesion either between the obtained lower electrode film and the substrate or between the lower electrode film and the piezoelectric layer at all.